Log_life

Storage lifespan with 20 GB (20,480 MB)
1 unit
20,480 ÷ 1.5 ≈ 13,653 days ≈ 37.4 years
10 units
15 MB/day → 20,480 ÷ 15 ≈ 1,365 days ≈ 3.7 years
25 units
37.5 MB/day → 20,480 ÷ 37.5 ≈ 546 days ≈ 1.5 years
50 units (worst case)
75 MB/day → 20,480 ÷ 75 ≈ 273 days ≈ 0.75 years

journalctl --vacuum-size=500M
journalctl --vacuum-time=30d
journalctl --vacuum-files=10
## Journal Vacuum
/etc/systemd/journald.conf
SystemMaxUse=500M        # total disk usage cap
SystemKeepFree=100M      # leave this much free space
SystemMaxFileSize=50M    # max size per journal file
MaxRetentionSec=30day    # max age

#logrotate:
/etc/logrotate.conf
$ cat /etc/logrotate.conf
# see "man logrotate" for details
# global options do not affect preceding include directives
# rotate log files weekly
weekly
# use the adm group by default, since this is the owning group
# of /var/log/syslog.
su root adm
# keep 4 weeks worth of backlogs ##
rotate 4
# create new (empty) log files after rotating old ones
create
# use date as a suffix of the rotated file
#dateext
# uncomment this if you want your log files compressed
#compress
# packages drop log rotation information into this directory
include /etc/logrotate.d

## actual log config:
$ cat /etc/logrotate.d/rsyslog
/var/log/syslog
/var/log/mail.info
/var/log/mail.warn
/var/log/mail.err
/var/log/mail.log
/var/log/daemon.log
/var/log/kern.log
/var/log/auth.log
/var/log/user.log
/var/log/lpr.log
/var/log/cron.log
/var/log/debug
/var/log/messages
{
	rotate 4
	weekly
	missingok
	notifempty
	compress
	delaycompress
	sharedscripts
	postrotate
		/usr/lib/rsyslog/rsyslog-rotate
	endscript
}